Solvent fractionation of waxcontaining mixtures



July 22, 195.2 E. w. CLARKE 2,604,434

SOLVENT FRACTIONATION OF WAX-CONTAINING MIXTURES Original Filed Sept. 16, 1947 2 -54 00/ r/ VE RAomnws EXT/V- SOLVENT 417551 I INZENTOR.

a G'Qs L'd arW Zarke 3 Au 2 [2/ Patented July 22, 1952 SOLVENT FRACTIONATI ON' OF WAX- CONTAINING MIXTURES Edgar W. Clarke, Laurel $prings,'N. J., assignor to The Atlantic Refining Gompany, Philadelphia, Pa., a corporation of Pennsylvania Original application September 16, 19.47, Serial a. 74 230 i i nd t sapmicatio November 1949, Serial No. 125,725

.3 claims. (01. '196-.-17)

. '1 The present invention relates to the treatment of oily waxes, and more particularly to the separation of -wax-containing mixtures into fractions "01f higher and lower melting point, using a solvent comprising acetone and an additiv comprising ethylene glycol mono-methyl ether.

This application is a division of copending application serial Number 774,230, filed September 16', 1947,,now Patent No. 2,578,510, and entitled Solvent Fractionation of Wax-Containing-Mixtures.

The present invention is especially applicable to the de-oiling of hydrocarbon waxes containlng'not more than about 70% of oil, and to the separation -of wax mixtures of low oil content into fractions of different melting point. In process of-the present invention may be applied in the refining, purification, or separation of wax stocks such as petroleum slack wax, crude microcrystalline wax, paraflin waxes, petrolatum wax, montan wax, ceresin, ozokerite, waxes from the destructiveor non-destructive hydrogenation of mineral oil, synthetic hydrocarbon oil, shale oil, coal, and waxes produced synthetically by the catalytic reaction of hydrocarbons, or waxes derived from the modified Fischer-Tropsch reaction of, carbon monoxide and hydrogen. The process of this invention is especially applicable in the separation of wax mixtures containing color bodies and oil into a higher melting wax fraction of light color and low oil content, and a lower melting wax fraction of darker color and containing most of the oil originally present in the wax mixture.

In accordance with this invention, a wax-con- The tain'ing mixture is separated into 'fractions of higher and lower melting point by countercurrently contacting the wax-containing mixture in an'extraction zone with an extraction solvent and a'solvent additive or additives at a temperature such that two liquid phases are formed, one. T

comprising the higher. melting wax fraction with minor amounts of solvent and additive, and the other comprising the lower melting: wax fraction with major amounts of solvent andadditive, separating the liquid phases from one an- .other, and removing the solvent and additive from each. a The extraction solvent employed may have a density less than that 'of' the wax, while the additive or additives may have a density greater than that of the wax the extraction solvent and will appear with that:

2 liquid phase comprising the higher melting wax fraction. The success of the process depends upon the control of the temperature throughout the extraction zone and upon th regulation of the proportions of solvent and additive used, and

' the points of introduction of the wax-containing mixture, the solvent, and the additive into the extraction zone.

, The extraction solvent may be defined as an agent which, when intimately mixed with a waxcontaining mixture, forms two liquid phases or layers, one comprising a ramnate phase containing mostly wax of higher melting point than the untreated wax and a portion of the solvent, and the other comprising an extract phase containing mostly solvent, and wax of lower melting point than the untreated wax, as well as major portion of the color bodies and 'oil originally present in the untreated wax.

The solvent additive may be defined as an agent used in conjunction with the extraction solvent for the purpos of modifying the characteristics of the extraction solvent. The additive may lower the temperature at which solid wax precipitates out of the extraction solvent, or it may raise the miscibility temperature of the extraction solvent with the wax. However, the additive chosen for a particular extraction solvent must not excessively lower the selectivity of the extraction solvent at the temperatureof extraction.

The extraction solvent may be employed in amounts ranging from 1 to 5 volumes of solvent per volume of untreated wax stock, while the 35 additive or additives may be used in amounts ranging from 0.05 to 1 volume per volume of untreated wax.

The extraction solvent which may be employed in accordance with the present invention comprises acetone.

The solvent additive or additives, which are usually employed in amounts constituting not more than 50% by volume of the extraction solvent, comprise ethylene glycol mono-methyl ether.

The process of the present invention may be carried out in a multi-stage batch countercurrent extraction system or in a continuous countercurrent extraction system, preferably a tower provided-with perforated bafiles or containing a packin material such as ceramic shapes, tiles, metalwool, or fragments of ceramic 'material, glass, pumic, Carborundum, or concrete. For most effective operation, a temperature gradient is maintained inithe system by means of heating or cooling coils or jackets, the. temperature in- 3 creasing in the direction of flow of the railinate or higher melting wax fraction.

The present invention maybe further understood with reference to the accompanying drawing which illustrates diagrammatically a continuous extraction system suitable for carrying out the process.

Referring to the drawing, a Wax-containing mixture is continuously introduced,'in liquid con; dition, into the extraction tower I through valve controlled pipe 2 at a rate of 100 volumes per hour. An extraction solvent comprlsing acetone is continuously introduced from vessel3 by means of valve-controlled pipe 4 and manifold 5 into thelower section of the tower'above the rafiinate outlet at a rate of 400 volumes per hour. The first additive comprising ethylene glycol mono-methyl ether is continuously introduced from vessel 6 through valve-controlled pipe I into the extraction tower l above the 'wax inlet at a rate of 40 volumes per hour. The second additive also comprising ethylene glycol mono-methyl ether is continuously introduced from vessel 9 by valve-controlled pipe 8 into the extraction tower 1 between the point of introduction of the first additive and the'outlet of the extract phase, at a rate of 40 volumes per hour. An intimate countercurrent contacting of the wax stock, the extraction solvent, and the additives is effected in tower l, the temperature being controlled in the tower by means of, coils ll through'which a heating or cooling medium is circulated as required. The temperature, in the present case,.is held constant,

, for example, at 85 R, the contents being entirely vin the liquid phase.

,jected to the action of the solvent and additives,

The wax stock, being sub- 1 and dissolved solvent and additive is passed from the bottom of tower I through valve-controlled .pipe l3 into a vacuum evaporator or still M wherein the solvent and additive is removed from the'higher melting wax by vaporization, the solvent and additive vapors passing through pipe 15 into fractionating tower 16 provided with a reboiler or heating coil [1, while the higher melt- I ing wax is drawn from the bottom of evaporator l4 and delivered by valve-controlled pipe I8 into storage vessel l9. Such wax fraction was white in color, andv had a substantially higher meltin point and a lower oil content than the wax stock originally charged.

The extract phase comprising the lower melting wax fraction, color bodies, oil, andthe major portion of the extraction solvent and additives is --withdrawn from the upper section of tower I The solvent and additive vapors are passed from'the top of evaporator 22 through pipe 25 into fractionating tower l5, wherein such vapors together with those introduced through pipe I5, are fractionated, the extraction solvent, i. e., acetone, being taken overhead as vapor through pipe 26, condensed in condenser 21 and returned by above the level of the dotted line 2!) representing,

the extract phase. relatively free of entrained,

higher melting wax. The extract phase is deliveredby valve-controlled pipe 2| into a vacuum --evaporator or still 22 wherein the solvent and additives are vaporized from the" lower melting,

wax, the latter being drawn from the bottom of V ,the evaporator and passedby valve-controlled pipe 23 to storage vessel 24. The lower melting pipe 28 to solvent storage vessel 3. A portion of the condensed solvent may be returned to the top of tower [6 by valve-controlled pipe 29 as reflux. The additive, i. e., ethylene glycol monomethyl ether, separated from the acetone by fractionation in tower I6, is taken from the bottom of tower l6, as liquid, and is returned by pipes 30 and 3| to the additive storage vessels 5 and 9.

Depending upon the temperature of operation, the first additive may be introduced somewhat below the point of introduction of the liquefied wax stock, for example, by means of valve-controlled pipe Hl rather than through. valve-controlled pipe vI, in which case the second additive may be admitted through'either or both of valvecontrolled pipes l and 8 above the point of introduction of thewaxstock. In general, the railinate wax phase withdrawn from the extraction tower will contain-from 5% to 25% of solvent and additive, while the extract Wax phase will contain from 55% to of solvent and additive.

In theevent that the extraction is to be carried out in a multi-stage batch countercurrent system, for example, a four-stage system using the solvent and additives specifically set forth above, the wax stock would be introduced into the first stage extractor, the extraction solvent (acetone) would be introduced into the fourth stage extractor, and the first additive, i. e., ethylene glycol monomethyl ether, would be introduced into the first stage extractor. The second. additive, e. g., ethylene glycol mono-methyl ether, would be introduced into the second stage extractor. The extract phase is withdrawn from the first stage, while the rafiinate phase would be removed from the fourth stage extractor. The temperature would increase progressively from the first stage to the fourth stage, using the waxy stock, solvent, and additives described hereinabove. It is to be understood, of course, that the quantities and composition of the solvent and of the additives may be varied within certain limits.

Exemplary of the solvent'and additive materials which may be used in'accordance with this invention is the following, the quantitiesbeing volumes per unit volume of wax stock.

Extraction Solvent 1st Additive 2nd Additive ethylene glycol monethylene. glycol 1n 0 n 0 m e t h yl ether 0.4=i- 0.1 vols.

I The present invention is further illustrated by the following example, which, however, is not to be construedas limiting the scopethereof;

- l (l) 'A slack Wax'having a melting point of 113 F. and an oil content of 24.2% by weight was extracted in a system similar tothat shown. in the accompanying drawing, the extraction solvent comprising 4 volumes of acetone, the first additive comprising 0.4 volume of ethylene glycol mono-methyl ether, and the second additive comprising 0 .4 volume of ethylene glycol monomethyl ether; The slack wax was introduced into tower I by pipe 2, the solvent by pipe 4 and manifold 5, the first additive by pipe I and the second additive by pipe 8. The temperature'in ethylene glycol monthe extraction tower was maintained constant atv 85 F. After countercurrent contacting and removal of the raihnate phase from the bottom of the tower, and the extract phase from. the top of the tower, the solvent and additives we're recovered from the wax fractions by vacuum evaporation and fractionation. The results are shown in the following table:

Where the extraction operation is conducted in a tower, it has been found that a tower having a height of about 40 feet and a diameter of 6 feet is satisfactory. The tower is provided with suitable packing to within about 4 feet of the top and bottom thereof, such spaces functioning as quiescent zones in which entrained materials are permitted to separate from the raffinate and extract phases, respectively. In such a tower, the wax stock is charged at a point about 13 feet from the top thereof, or approximately the distance from the top of the tower. The extraction solvent is charged just above the lower level of the packing, for example, 3 to 4 feet from the bottom of the tower. The first additive may be introduced adjacent the point of introduction of the wax stock, for example, 2 feet above or below the wax inlet. The second additive is introduced approximately 2 feet above the point of introduction of the first additive. These values may be altered somewhat, depending upon the tower design, the solvent and additives used, and the temperatures maintained at various levels in the tower. The raffinate phase is withdrawn from the bottom of the tower, and the extract phase from the top thereof, the extraction solvent being less dense than the wax stock.

I claim:

1. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises countercurrently contacting said wax-containing mixture in an extraction zone with an extraction solvent and solvent additives at a temperature such that two immiscible liquid phases are formed, one comprising the higher melting wax fraction containing solvent and additives, and the other comprising solvent and additives and the lower melting wax fraction, separating the phases from one another, and removing the solvent and additives from each, the solvent being introduced into the extraction zone near the point of withdrawal of the higher melting wax fraction, the first additive being introduced adjacent the point of introduction of the wax-containing mixture, and

the second additive being introduced between the point of introduction of the first additive and the point of Withdrawal of the lower melting wax fraction, the solvent comprising 3.5 to 4.5 volumes of acetone per volume of wax-containing mixture, the first additive comprising 0.3 to 0.5 volume of ethylene glycol mono-methyl ether per volume of wax-containing mixture, and the second additive comprising 0.3 to 0.5 volume of ethylene glycol mono-methyl ether per volume of wax-containing mixture.

2. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises countercurrently contacting said wax-containing mixture in an extraction zone with an extraction solvent and solvent additives at a temperature such that two immiscible liquid phases are formed, one comprising the higher melting wax fraction with minor amounts of solvent and additives, and the other comprising the lower melting wax fraction with major amounts of solvent and additives, separating the phases from one another, and removing the solvent and additives from each, the solvent being introduced into the extraction zone near the point of withdrawal of the higher melting wax fraction, the first additive being introduced between the point of introduction of the wax-containing mixture and the point of withdrawal of the lower melting wax fraction, and the second additive being introduced between the point of introduction of the first additive and the point of withdrawal of the lower melting wax fraction, the solvent comprising 3.5 to 4.5 volumes of acetone per volume of wax-containing mixture,

' the first additive comprising 0.3 to 0.5 volume of ethylene glycol mono-methyl ether per volume of Wax-containing mixture, and the second additive comprising 0.3 to 0.5 volume of ethylene glycol mono-methyl ether per volume of wax-containing mixture.

3. The method of separating a wax-containing mixture into fractions of higher and. lower melting point, which comprises countercurrently contacting said wax-containing mixture in an extraction zone with an extraction solvent and solvent additives at a temperature such that two immiscible liquid phases are formed, one comprising the higher melting wax fraction containing solvent and additives, and the other comprising solvent and additives and the lower melting wax fraction, separating the phases from one another, and removing the solvent and additives from each, the solvent being introduced into the extraction zone near the point of withdrawal of the higher melting wax fraction, the first additive being introduced adjacent the point of introduction of the wax-containing mixture, and the second additive being introduced between the point of introduction of the first additive and the point of withdrawal of the lower melting wax fraction, the solvent comprising 3.5 to 4.5 volumes of acetone per volume of wax-containing mixture, the first additive comprising 0.3 to 0.5 volume of ethylene glycol mono-methyl ether per volume of wax-containing mixture, and the second additive comprising 0.3 to 0.5 volume of ethylene glycol mono-methyl ether per volume of wax-containing mixture.

EDGAR W. CLARKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,017,432 Bahlke Oct. 15, 1935 2,063,369 Diggs et a1. Dec. 8, 1936 2,160,930 Whiteley et a1 June 6, 1939 2,178,078 Martin Oct. 31, 1939 2,541,338 Clarke Feb. 13, 1951 

1. THE METHOD OF SEPARATING A WAX-CONTAINING MIXTURE INTO FRACTIONS OF HIGHER AND LOWER MELTING POINT, WHICH COMPRISES COUNTERCURRENTLY CONTACTING SAID WAX-CONTAINING MIXTURE IN AN EXTRACTION ZONE WITH AN EXTRACTION SOLVENT AND SOLVENT ADDITIVES AT A TEMPERATURE SUCH THAT TWO IMMISCIBLE LIQUID PHASE ARE FORMED, ONE COMPRISING THE HIGHER MELTING WAX FRACTION CONTAINING SOLVENT AND ADDITIVES, AND THE OTHER COMPRISING SOLVENT AND ADDITIVES AND THE LOWER MELTING WAX FRACTION, SEPARATING THE PHASE FROM ONE ANOTHER, AND REMOVING THE SOLVENT AND ADDITIVES FROM EACH, THE SOLVENT BEING INTRODUCED INTO THE EXTRACTION ZONE NEAR THE POINT OF WITHDRAWAL OF THE HIGHER MELTING WAX FRACTION, THE FIRST ADDITIVE BEING INTRODUCED ADJACENT THE POINT OF INTRODUCTION OF THE WAX-CONTAINING MIXTURE, AND THE SECOND ADDITIVE BEING INTRODUCED BETWEEN THE POINT OF INTRODUCTION OF THE FIRST ADDITIVE AND THE POINT OF WITHDRAWAL OF THE LOWER MELTING WAX FRACTION, THE SOLVENT COMPRISING 3.5 TO 4.5 VOLUMES OF ACETONE PER VOLUME OF WAX-CONTAINING MIXTURE, THE FIRST ADDITIVE COMPRISING 0.3 TO 0.5 VOLUME OF ETHYLENE GLYCOL MONO-METHYL ETHER PER VOLUME OF WAX-CONTAINING MIXTURE, AND THE SECOND ADDITIVE COMPRISING 0.3 TO 0.5 VOLUME OF ETHYLENE GLYCOL MONO-METHYL ETHER PER VOLUME OF WAX-CONTAINING MIXTURE. 